Genuine Daikin 4015679 Outdoor Expansion Valve Coil is the electrical coil that drives the outdoor electronic expansion valve, moving it to the position the control board calls for to meter refrigerant flow. When it fails, the valve may not move correctly and the outdoor unit can lose output, ice up, or stop and start at odd times. A genuine coil drives the valve the way your Daikin expects, keeping flow control accurate — where a non-genuine part can drive it weakly or unreliably.